Apparatus for blood plasma separation

ABSTRACT

An apparatus for centrifugally separating blood plasma from red blood cells, said apparatus being adapted for use with a blood bag set composed of a pair of mother bags and a daughter bag communicating therewith, said apparatus comprising a blood bag receiving box of generally inverted V-shape cross section having a pair of bottom plates hinged for upward movements, rotary drum, flywheel of larger inertia than that of the drum and a mechanism operable, after completion of blood plasma separation within said mother bags and after switching off of the power source of the apparatus, to upwardly urge the bottom plates of the blood bag box against the cover thereof by virtue of the difference in inertial rotation between the drum and the flywheel to thereby automatically squeeze the separated fluid of blood plasma out of the mother bags into the daughter bag.

United States Patent Primary ExaminerWilliam l Price Attorney-Christen,Sabol ABSTRACT: An apparatus for centrifugally separating blood plasmafrom red blood cells, said apparatus being adapted for use with a bloodbag set composed of a pair of mother bags and a daughter bagcommunicating therewith, said apparatus comprising a blood bag receivingbox of generally inverted V- shape cross section having a pair of bottomplates hinged for upward movements, rotary drum, flywheel of largerinertia than that of the drum and a mechanism operable, after completionof blood plasma separation within said mother bags and after switchingoff of the power source of the apparatus, to upwardly urge the bottomplates of the blood bag box against the cover thereof by virtue of thedifference in inertial rotation between the drum and the flywheel tothereby automatically squeeze the separated fluid of blood plasma out ofthe mother bags into the daughter bag.

[72} inventors Ryoichi Naito;

Osamu Yamaji, Osaka, Japan [21] Appl. No. 795,934 [22] Filed Feb. 3,1969 [45] Patented Feb. 2, 1971 [73] Assignee The Green CrossCorporation Osaka, Japan a corporation of Japan 7 [32] Priority Oct. 3,1968 [33] Japan [31] 43/86264 [54] APPARATUS FOR BLOOD PLASMA SEPARATION1 Claim, 14 Drawing Figs.

[52] [1.8. CI.. 233/26 [51] Int. Cl B04b 1/00, B04b 9/14 [50] Field ofSearch 233/1, 26, 17, 27, 28

[56] References Cited UNITED STATES PATENTS 3,211,368 10/1965 Shanley233/26 PATENTED FEB 2197: 3559.880

sum 1 0F 5 PRIOR A T PATENTEUFEB 21911 3559880 saw u [1F 5 I I APPARATUSFOR BLOOD PLASMA SEPARATION BACKGROUND OF THE INVENTION Field of theInvention This invention relates to an apparatus for blood plasmaseparation, and more particularly. to an apparatus for centrifugallyseparating blood into red blood cells and fluid of plasma.

Blood comprises corpuscles mostly of red blood cells and fluid of plasmarich in proteins. Once blood is taken out from the body, red blood cellshardly survive long, whereas plasma can be preserved for a long periodof time and can further be fractionated and purified into several usefulpreparations according to the respective specific properties of eachprotein fraction. It is a well-known fact in physiology that plasmaproteins are replenished in the body within a short time after blooddonation but red blood cells require a rather long time for theirreconstitution. From the viewpoint of donor's health, therefore, it isadvisable that red blood cells be separated from liquid of plasma andreturned back=into the circulation of the donor.

The series of procedures; collection of blood from vein of a donor intoa container with anticoagulant, separation of plasma, resuspension ofred blood cells and giving back of the suspension into the vein of thedonor, are called as plasmapheresis" in this field and becomingcommonner in practice.

For this reason, a variety of methods have already been developed forseparation of blood plasma. They are roughly classified into followingtwo categories:

I. A method using glass bottle; and

2. A method using flexible and soft blood bag.

1. Glass bottle method A glass bottle of 500 ml. capacity and containingI percent aqueous sodium citrate solution is sterilized and used as ablood container for bleeding, into which blood is collected from thevein of a donor. After separation of red blood cells and plasma by meansof centrifugal separator, the supemate is taken out through a finetubing, leaving the packed red blood cells at the lower part of thebottle. Normal saline or other equivalent solution is added to suspendthe red blood cells and return the suspension to the vein of the donor.

2. Flexible blood bag method A blood bag such as one shown in FIG. 1 isusually used. The blood bag is made of polyvinyl chloride or otherqualitatively equivalent material for flexibility of the bag. The bag iscomposed of a mother bag I, a daughter bag 2 and a tubing 3interconnecting them. The mother bag is added with an anticoagulantsolution such as sodium citrate solution and is sterilized. Venous bloodis collected in the mother bag through a short tubing 4 connecting avenous needle and the mother bag. The bag is then mounted on acentrifuge and rotated thereby with the tubing 3 collapsibly closed andwith an outlet 5 disposed close to the rotatory shaft whereby most ofthe red blood cells are gathered at the bottom 6 of the mother bag.After the centrifugation and stop of the centrifuge, the mother bag isplaced between and pressed with two hinged transparent boards forsqueezing the plasma out of the mother bag through the outlet 5 and thetubing 3 into the daughter bag 2. The tubing is cut to separate thedaughter bag containing the plasma from the mother bag. The latter issupplied with normal saline to suspend the packed red blood cells andreinfuse to the donors vein. It is generally accepted that, as comparedwith the glass bottle method, this blood bag method maintains bettersterility during the procedures in ad dition to its causing less damagesto the red blood cells because of flexibility of bags and connection ofa mother bag and a daughter bag through tubing.

Whichever method may be employed, to 30 minutes are required for theprocedures in which the blood collected from a donor is subjected tocentrifugal separation of plasma by use of a centrifuge which hasoperative acceleration and deceleration stages in rotational speed.Thus, the donor suffers from a mental pain in having a long wait andfrom a physical pain in holding a bleeding needle in the vein for a longtime.

SUMMARY OF THE INVENTION It is, therefore, a primary object of thepresent invention to provide an improved blood plasma separationapparatus which is designed to be used with a flexible blood bag set consisting of mother and daughter bags and containing blood collected fromdonors and which is operable to centrifugally separate the blood intored blood cells and fluid of plasma and, after switch-off of the powersource of the apparatus, automatically press the mother bags forsqueezing out the separated fluid of plasma therefrom during inertialrotation of the apparatus thereby to greatly shorten the time requiredfor transfer of plasma.

According to the present invention, there is provided an ap' paratus forseparating fluid of blood plasma from red blood cells, said apparatusbeing adapted for use with a blood bag set composed of a pair of motherbags and a daughter bag communicated therewith, said apparatuscomprising a box of substantially inverted V-shape for receiving saidblood bag set in such a manner that said mother bags extend outwardlydownwardly in diametrically opposite directions and said daughter baghangs down, said box having bottom plates hinged for upward movement, amain rotary body on which said box is mounted, a flywheel of largerinertia rotatably mounted onto said rotary body for free rotation withina predetermined range, substantially vertical levers pivotably connectedto said rotary body and having their upper ends in contact with saidbottom plates of said blood bag box, horizontal levers pivotably mountedat one ends onto said flywheel and having recesses therein, saidvertical levers having their lower ends received in said recesses insaid horizontal levers, respectively, tension springs connected to theother end of said horizontal levers for biasing same inwardly towardsaid rotary body, said horizontal levers having shoulders in the innerfaces thereof next to said recesses toward said the other ends whereby,upon outward displacement of said horizontal levers due to centrifugalforce, said lower ends of said vertical levers are brought intoengagement with said shoulders of said horizontal levers.

BRIEF DESCRIPTION OF THE DRAWINGS Other objects and features of thepresent invention will be made apparent from the following descriptionin conjunction with the accompanying drawings, and in which:

FIG. 1 schematically illustrates, in perspective view, a commonly usedprior art blood bag set;

FIG. 2 is a view similar to FIG. 1 but illustrating a blood bag setaccording to the present invention;

FIG. 3 is a vertical sectional view of an embodiment of the blood plasmaseparation apparatus according to the present invention;

FIG. 4 is a plan view of a rotary section of the apparatus shown in FIG.I with a part removed away;

FIG. 5 is a perspective view of a frame for holding a blood bagreceiving box;

FIG. 5A is a cross-sectional view taken along line VA-VA in FIG. 5;

FIG. 5B is a cross-sectional view taken along line VB-VB in FIG. 5;

FIG. 6 is a perspective view of the blood bag receiving box;

FIG. 7 is a fragmentary perspective view showing a cover of the bloodbag receiving box in FIG. 6 and means for fastening the cover, withparts removed and cut away;

FIG. 8 illustrates in plan view engagement between vertical andhorizontal levers;

FIG. 9 is a view similar to FIG. 8 but illustrating the levers inslightly different position;

FIG. 10 illustrates in vertical section the levers in the position shownin FIG. 9;

FIG. 11 is a view similar to FIG. 9 but illustrating the levers infurther different position; and

FIG. 12 illustrates in vertical section the levers in the position shownin FIG. 11.

DESCRIPTION OF PREFERRED EMBODIMENT Referring now to FIG. 2, the bloodbag set according to the present invention is indicated generally at 10and comprises a pair of mother bags 11, 11' communicating with eachother through an intermediate or bridge portion 11a interconnecting themother bags at their tops, a small daughter bag 12 disposed between themother bags and a pair of tubings 13, 13 connecting the daughter bag 12to the bridge portion 11a for communicating the interiors of the motherbags with that of the daughter bag. The mother bags 11, 11' areconnected with short tubings 14, 14' adapted to be connected withbleeding needles through appropriate tubings, respectively. Formedcentrally of the bridge portion 11a are openings in'the top and thebottom walls of the bridge portion. The peripheral edges of the openingsare heat-sealed together. A ring 15 is fitted to the sealed edge of theopening. The blood bag set 10 is made of polyvinyl chloride or the likematerial. Preferably, the material is transparent or sernitransparentfor enabling one to observe the interiors of the bags from the outsidethereof. Also, the material is required to withstand a steam pressuresterilization at 121 C. for 30 minutes. The whole bag set is subjectedto a heat sterilization after putting of an anticoagulant solution, suchas aqueous solution of sodium citrate or heparin, of properconcentration into the mother bags. For collection of blood, all bags ofa set are placed in a closed container, whose inner pressure is thenreduced. A negative atmospheric pressure sucks the blood from the veinof a donor through a bleeding needle and one of the short tubings 14,14' into the mother bags. During the bleeding, the tubings l3, 13' arepressed and closed with a clamp to prevent the blood from flowing intothe daughter bag 12. The blood collected in the mother bags 11, 1 l iswell mixed with the anticoagulant solution and is divided equally intotwo masses to balance the mother bags.

A description will next be made, with reference to FIGS. 3 to 7, of acentrifugal machine according to the present invention and adapted to beused with the blood bag set 10 shown in FIG. 2. Referring first to FIG.3, there is shown an embodiment of the centrifugal machine generallydesignated at 20. The machine includes a base 21 housing therein anelectric motor (not shown) having its shaft 22 projecting upwardly. Ontothe top of the base 21 is secured a generally cylindrical casing 23having an open top. An annular fitting 24 is mounted by means of boltsand nuts on the casing 23 around the opening in the top thereof. Fittedto the annular fitting 24 is an annular shock-absorbing air-tube 25 overwhich is detachably mounted a cover 26 having a bearing 27 mounted in acentral aperture in the cover. The bearing 27 is adapted for rotatablyreceiving therein a shaft 28 for the purpose which will be describedlater.

Within the casing 23 is disposed a bottomed drum 30 having a boss 31extending downwardly from the bottom through which the motor shaft 22extends upwardly into the interior of the drum. The latter is fastenedto the motor shaft by means of a nut 29. The drum 30 has, at theintermediate portion of the height, a radially outwardly projectingannular flange which is cut at diametrically opposite sides to form twosubstantially arcuate flanges 32, 32' and two straight and parallelsurface 33, 33' as shown in FIG. 4. The distance from the center of thedrum 30 to each of the surfaces 33, 33 is the same as the outer radiusof the drum as measured at the portion just above the flanges 32, 32'.The drum 30 is also provided with two pairs of radial projections 34 and34. The arcuate flanges are respectively formed, at central portions,with notches 32a, 32a having their bottoms extending outwardlydownwardly, the center of the notch in each of the flanges 32, 32' beingin vertical alignment with the center of each pair of the radialprojections.

A substantially rectangular frame 35 is secured to the drum 30 by meansof a ring 36 threadably engaging the upper portion of the drum. Morespecifically, the frame 35 includes two longitudinal bars 35A, 35A,lateral bars 35B, 35B interconnecting the bars 35A, 35A at the oppositeends thereof and a lateral bridge 35C interconnecting the longitudinalbars at the central portion of the frame 35 as best seen in FIG. 5. Thebridge 35C is coplanar at thetop surface, with the top surfaces of thebars 35A, 35A, 35B, 358 but is substantially one half in thickness thebars, as shown in FIGS. S-A and 5-8. The bridge 35C is fon'ned-thereinwith an annular opening whose diameter is the same as the distancebetween the inner surfaces of the longitudinal bars 35A, 35A, whichdistance is, in turn, the same as or slightly larger than the diameterof the drum 30 as measured at the portion just above the flanges 32.32'. It will, thus, be apparent that, when the frame 35 is mounted overthe drum 30, the annular opening in the bridge 35C of the frame 35snugly receives the upper portion of the drum with the bottom surface ofthe bridge in contact with the upper shoulders of the arcuate flanges32, 32' and with the inner surfaces of the frame bars 35A, 35A atlongitudinally intermediate portions of the surfaces tightly contactingthe opposite parallel surfaces 33, 33' of the drum 30. When the ring 36is fastened downwardly on the drum 30, therefore, the frame 35 isrigidly connected to the drum for rotation therewith.

The frame 35 further includes a pair of cars 35D, 35D connected to theouter surfaces of the longitudinal bars 35A, 35A centrally thereof.Studs 35E, 3515' having enlarged heads are rigidly planted in the ears35D, 35D for the purpose described later. In addition, the bridge 35C ofthe frame 35 has downwardly outwardly inclined outer surfaces'and isalso provided with a pair of notches 35C, 35C" in the inclined outersurfaces centrally thereof, respectively. The bottom surfaces of thenotches 35C, 35C incline downwardly inwardly, as best seen in FIG. 5-B.Thus, it will be appreciated that, when the frame 35 is mounted inposition on the drum 30, one of the notches in the arcuate flanges 32,32 and one of the notches 35C, 35C" in the frame bridge 35C are invertical alignment and the inclined bottom surfaces of the verticallyaligned notches cooperate to define two recesses in the combined drum 30and frame 35 for the purpose described hereinafter.

The pairs of projections 34, 34' have pins 36, 36', respectively, onwhich two-armed generally vertical levers 37, 37' are pivotably mountedat substantially intermediate points of their lengths. The levers 37,37' are respectively provided with rollers 38, 38' at their upper ends.The length of each of the lever 37, 37 between its pivotal axis and theupper end is dimensioned such thatthe upper roller 38 or 38' is receivedby and rests in the recess defined by the inclined bottom surfaces ofthe notches in the arcuate flange 32 or 32' and in the bridge 35C of theframe 35.

A flywheel 40 is mounted around the boss 31 of the drum 30.Specifically, the wheel 40 has a central boss 41 which extends upwardlyfrom the bottom of the wheel 40 and which surrounds a unit of rotary andthrust bearing 42 disposed around the drum boss 31. A nut 42a isdisposed around the drum boss 31 under the bearing unit 42 for rotatablysupporting the flywheel assembly on the drum 30.

A pair of elongated arcuate horizontal levers 43, 43 are disposedradially outwardly of the vertical levers 37, 37, respectively, and havetheir one ends pivotally connected by means of pins 44, 44" on thebottom of the flywheel 40 ad jacent the upstanding peripheral wallthereof. The other end of each horizontal lever is connected with atension spring 45 or 45' anchored on the flywheel bottom on the pointsubstantially diametrically opposite to the pivotal axis of thehorizontal lever so as to pivotally move the free end thereof inwardlytoward the drum 30 about the pin 44 44. Stops 46, 46' are provided onthe flywheel bottom adjacent the free or forward ends of the horizontallevers 43, 43' for preventing the free ends of the horizontal leversbeyond a predetermined range. The horizontal levers are formed withrecesses 47, 47 of substantial width and having inwardly downwardlyinclined bottomsurfaces for receiving lower rollers 39, 39' of thevertical levers 37, 37'. Each of the horizontal levers is thinned at theportion next to the recess 47 or 47 and then widened or enlarged to forma step or shoulder 48 or 48 with which the lower roller 39 or 39' ofcorresponding vertical lever is brought into engagement when thehorizontal levers are moved outwardly against the tension springs 45,45' by centrifugal force. It will thus be noted that the horizontallevers rotate with the flywheel about the rotational axis thereofrelative to the vertical levers as will be described in detailhereinafter. Rotatably mounted around the flywheel boss 41 is a ring 49having diametrically opposing projections 49a,49b which are linked tothe free ends of the horizontal levers 43, 43'. respectively, by meansof link rods 50, 50 whereby the pairs of horizontal levers arecontrolled to have equalized movements.

Disposed over the drum 30 is a blood bag receiving box or containergenerally designated at 50 in F IG. 3. The box 50 has generally rooflikeor inverted V-shape cross section and is composed of a body 51 and acover 52. As will be seen in FIG. 6, the body 51 of the blood bag box 50has opposite side plates or walls 53, 53' of generally inverted V-shapeand generally rectangular opposite end walls 54, 54 interconnecting theopposite sidewalls at their opposite ends. Disposed between the oppositesidewalls 53, 53 are spaced intermediate plates 55, 55 of substantialthickness for interconnecting the sidewalls at their intermediateportions. The intermediate plates have outwardly downwardly inclinedupper surfaces and horizontal bottom surfaces. A pair of bottom plates56, 56' are connected to the intermediate plates 55, 55 respectively bymeans of hinge means 57, 57 for upward swinging movements. The innersurfaces of the end plates 54, 54 are arcuate for this purpose. Thesidewalls 53, 53 are formed with larger notches 58, 58 at the top apecesand small notches 59, 59 adjacent the notches 58, 58', respectively. forthe purpose which will become apparent later. The sidewalls have theirhorizontal bottom edges in the plane in which the bottom surfaces of theintermediate plates 55, 55 extend. The horizontal bottom edges of thesidewalls 53, 53' have the dimension the same as or slightly larger thanthe outer diameter of the drum 30 as measured on the top thereof.Furthermore, each of the end walls 54, 54 is partly cut so as to form avertical plane, the distance between the vertical planes in the oppositeend plates 54, 54 being the same as or slightly smaller than thedistance between the inner surfaces of the lateral bars 35B, 35B in theframe 35. It will, thus, be appreciated that, when the blood bag boxbody 51 is disposed over the drum 30, the bottom surfaces of theintermediate plates 55, 55' are supported by the top of the drum 30 andthe vertical planes in the end plates 54, 54 of the box body 51 tightlycontact the inner surfaces of the lateral bars 35B, 35B of the frame 35.with the bottom plates 56, 56' of the box 50 being in contact with andsupported by the inclined surfaces of the bridge 35C of the frame 35 andthe upper roller 38, 38 of the vertical levers 37, 37. The side plates53, 53 of the body 51 of the box 50 are shaped such that, verticalplanes in the end plates 54, 54 engage the inner surfaces of the lateralbars 35B, 35B in the lower halves thereof.

The cover 52 of apparent blood bag container 50 is dimensioned andshaped to match the size and configuration of the body portion 51 of thecontainer and has a pair of parallel side plates 53a, 531: as seen inFIG. 7. a pair of vertical end walls 54a, 54a as seen in FIG. 3 and atop plate 561/ ofa single piece structure. In the illustratedembodiment, the end walls 540,541! and the top plate 5611 are formedintegrally. but they may be formed separately. A disc 71 is rigidlysecured to the top plate 56a on the apex and centrally thereof. A hole72 is formed through the plate 71 and the top plate 560. Each of theside plates 53, 53a is formed with a semicircular notch 59a, 5911 (onlythe note 5911' is shown in H6. 3) at a location corresponding to that ofthe notch 59 or 59 in each of the side plates 53, 53 of the body 51. Itwill. therefore. be apparent that, when the cover 52 is mounted over thebody 51 in the machine 20. the side plates 53a, 53a and end walls540,541! of the cover snugly ride on the corresponding parts in thecontainer body 51 with the outer surfaces of the end walls and a part ofthe outer surfaces of the side plates in close contact with the innersurfaces of the lateral bars 35B, 35B of the frame 35 in the remainingupper halves of the bar surfaces. It will also be apparent that, in thisposition of the box 50, the two pairs of notches 59 and 5911; 59' and59a define two annular openings, one of which is seen in FIG. 3.

A rod 60, having notches in the opposite sides adjacent the oppositeends thereof. spans the studs 35E, 35E above the cover 52 of the bloodbag 50 with said notches receiving therein the shanks of the studs 35E,35E. as will be seen in FlG. 7. As will be seen in FIG. 3, the rod 60 isformed, at the intermediate portion, with a threaded hole 61 with whichthe above-mentioned shaft 28 engages at its threaded portion 28a. Theshaft 28 further has a reduced lower portion 28b extending downwardlyfrom the threaded portion 28a into the interior of the blood bag box 50through a hole 72 in the disc 71 on the top plate 56a of the cover 52.Thus, it will be noted that the shaft 28 has a downwardly facing annularshoulder which engages the top surface of the disc 71. it will befurther noted that, when the shaft 28 is rotated in one of thedirections, it is moved down relative to the rod 60 to press the disc 71downwardly for rigidly holding the cover 52 of the box 50 against upwardseparation from the body portion 51 of the box. In this state, the uppersurface of the rod 60 is urged against the under surfaces of theenlarged heads of the studs 35E, 35E.

A description will be made hereunder of the operation of theabove-described centrifugal machine.

When it is desired to place the blood bag set 10 in the centrifugalmachine 20, the shaft 28 is loosed to disengage the rod 60 from thestuds 35E, 35E) and to remove the rod 60 together with the cover 26 fromthe machine. Then, the cover 52 of the blood bag box 50 is lifted awayfrom the body 51 of the box and from the supporting frame 35. Then, theabovedescribed blood bag set 10 is placed in the box 50 in such a mannerthat the mother bags 11, 11' extends downwardly and outwardly along thebottom plates 56, 56 of the box body 51, respectively. with the shorttubings 14, 14' received in the notches 59, 59 in the box side plates53, 53' and extending therethrough into the exterior of the box 50,respectively, and that the daughter bag 12 extends downwardly into theinterior of the drum 30, with the curved portions of the connectingtubes 13, 13 received in the notches 58, 58' in the side plates 53, 53.In this position of the blood bags, the clips on the connecting tubingsl3, 13 are removed so as to provide communication between the interiorsof the mother and daughter bags. The cover 52 is then placed over thebox body 51 and is fastened by means of the shaft 28, the rod 60 and thepair of studs 35E, 35E: in the manner as described in the above. It willbe noted that, when the shaft 28 is screwed down, the reduced diameterlower end 28b of the shaft 28 extends through the ring 15 on the bloodbag set 10 contained in the box 50.

Upon completion of the above preparation, the motor of the machine isswitched on to rotate its shaft 22 and thus the drum 30 connectedthereto. The rotation of the drum is transmitted by the frame 32 mountedthereon to the blood bag box 50 and thus to the blood bag set 10contained in the box with the mother bags 11, 11 held in inclined state.The machine is operated at 2,000 to 3,000 rpm. The blood in the motherbags is, thus, subjected to centrifugal force by which the red bloodcells are gradually moved down and collected in the bottom portions l6,16 of the mother bags 11, 11 whereas the fluid of the blood plasma isgathered in the upper portions of the bags due to the difference inspecific gravity between the red blood cell and the plasma.

At the start of the operation of the centrifugal machine, each of thehorizontal levers 43, 43 are in their innermost positions in which theyare held in contact with the stops 46,

46' by the tension springs 45, 45'. respectively. and in which the lowerrollers 39, 39' of the vertical levers 37. 37' are positioned on theradially outer edges of the recesses 47. 47' in the levers 43, 43',respectively, as seen in FIG. 4. The rotation of the drum 30 indicatedby an arrow in FIG 8 causes the vertical levers to urge. at the lowerends, the horizontal levers in counterclockwise direction, which in turnrotates the flywheel 40 in the same direction. As the rotational speedof the drum increases, the horizontal levers 43, 43 are moved outwardlyagainst the springs 45, 45' by the centrifugal force, whereas the lowerrollers 39, 39' remain engaging the recesses 47, 47' even at high speedrotation (FIG, 8).

After a predetermined period of time known from ex' perience as beingsufficient for the red blood cells to be completely separated out fromthe liquid of blood plasma. the motor is switched off. The machinecontinues rotating due to inertia in such a manner that the rotationalspeed is gradually reduced by the resistances of air and frictiongenerated between mechanical elements. However, the flywheel has agreater inertia and, thus, has a smaller deceleration as compared withthose of the rotary drum 30. This produces a relative rotation betweenthe flywheel and the drum. Namely, the rotary drum becomes to have alower speed than that of the flywheel, so that the rollers 39, 39' aredisengaged from their recesses 47, 47' in the horizontal levers 43, 43'down into inside of the latter and are brought into engagement with theshoulders 48, 48 of the levers as shown in FIGS. 9 and 10. Thereafter,the inertial rotation of the flywheel as indicated by an arrow b in FIG.9 is transmitted through the horizontal and vertical levers 43, 43'; 37,37 to the drum 30 for rotating the latter together with the flywheel.

The speed of the flywheel is slowed down in a while and the centrifugalforce in the horizontal levers are reduced so that the springs 45, biasthe free ends of the levers inwardly. these inward movements of thehorizontal levers urge the lower rollers 39, 39' of the vertical levers37, 37 inwardly to cause them to rotate about their pivotal axes or pins36, 36' whereupon the upper rollers 38, 38 of the vertical leversupwardly urge the bottom plates 56, 56' of the blood bag box 50 to pressthe mother bags 11, 11' between the bottom plates and the top plate 56aof the box 50. Thus, the fluid of blood plasma is squeezed out of themother bags 11, 11 through tubings 13, 13 into the daughter bag 12. Thearrangement of the above structural elements is such that, when thehorizontal levers 43, 43 are moved to their innermost positions in whichthey contact their stops 46, 46 almost all of the liquid of blood plasmaare removed from the mother bags 11, ll into the daughter bag 12 leavingthe red blood cells with the mother bags.

At about a time the blood plasma separation is completed, the flywheelstops its rotation. Then, the cover 52 of the blood bag box 50 isremoved in the above-described manner to replace the blood bag set 10from the machine. The lower rollers 39. 39' of the vertical levers 37,37 are manually shifted from the shoulders 48, 48' of the horizontallevers 43, 43' into the recesses 47, 47' therein for the next operation.

Thus, it will be appreciated that, with the apparatus of the presentinvention, blood plasma separation is completed during the period fromthe time the motor of the centrifugal machine is switched off to thetime the rotation of the machine stops.

The present invention has been described with reference to a preferredembodiment. It is to be understood that the embodiment above describedis only for illustrative purpose and the present invention may havevarious modifications and changes within the scope and spirit of theinvention which is defined by the appended claims. For example. the setof blood bag 10 in FIG 1 may be provided with a pair of additionaltubings each interconnecting the mother bags 11 and 11' at their lowerends for balancing the quantities of the blood contained therein duringinitial stage of centrifugal operation. in addition, the casing 23 inFIG. 3 may be provided around the cylindrical wall thereof with acircular jacket through which cooling liquid, such as ethyleneglycol, ofa temperature ranging from 2 to 3 C may be circulated for maintainingthe temperature in the casing and thus of the blood in the blood bags inthe casing lower than about 10 C. during centrifugal separation of theblood.

We claim:

1. An apparatus for separating fluid of blood plasma from red bloodcells, said apparatus being adapted for use with a blood bag setcomposed of a pair of mother bags and a daughter bag communicatedtherewith, said apparatus comprising a box of substantially invertedV-shape for receiving said blood bag set in such a manner that saidmother bags extend outwardly downwardly in diametrally oppositedirections and said daughter bag hangs down, said box having bottomplates hinged for upward movement, a main rotary body on which said boxis mounted, a flywheel of larger inertia rotatably mounted onto saidrotary body for free rotation within a predetermined range,substantially vertical levers pivotably connected to said rotary bodyand having their upper ends in contact with said bottom plates of saidblood bag box horizontal levers pivotably mounted at one ends onto saidflywheel and having recesses therein, said vertical levers having theirlower ends received in said recesses in said horizontal levers,respectively, tension springs connected to the other end of saidhorizontal levers for biasing same inwardly toward said rotary body,said horizontal levers having shoulders in the inner faces thereof nextto said recesses toward said the other ends whereby, upon outwarddisplacements of said horizontal levers due to centrifugal force, saidlower ends of said vertical levers are brought into engagements withsaid shoulders of said horizontal levers.

